Advanced Materials Research Vol. 1124

Abstract: The paper deals with possibilities of application of hydrophobised waterproof walling system for construction of building bottom parts (socle walling) in area with higher risk of floods. The paper describes the results from the research in the field of hydrophobisation possibilities of ceramic shaped pieces and subsequent development of socle waterproof walling construction.

Abstract: The corrosion of steel elements in reinforced concrete can cause considerable damage to civil engineering structures. Early detection of corrosion is therefore very important. Steel in concrete is protected if the concrete pH is higher than 9.6. Carbonated concrete, unfortunately, has a lower pH and this causes that the unprotected steel reinforcement begins to corrode. Nonlinear ultrasonic spectroscopy (NUS) methods shows potential to be very reliable to identify the structure defects in a wide range of materials. These methods are based on the fact that crack-induced nonlinearity makes a sensitive material impairment indicator. This paper describes the ability of one of NUS methods for monitoring steel corrosion in reinforced concrete. It studies nonlinear interaction between elastic waves and structural defects caused by corrosion of steel in concrete. For research we used concrete beams with ten millimetres thick steel rods. These beams were exposed to accelerated degradation by chlorides. The paper presents the initial results of our research.

Abstract: Ultrasonic non-destructive testing methods such as Impact-echo are often conducted under different conditions. Such results might be distorted by ambient temperature or by water content of the tested sample. Tested mortar sample displayed shift of the fundamental frequency by 3.7 %. This article confirms necessity of standardized conditions during ultrasonic testing for both laboratory and in-situ testing.

Abstract: Maximum Length Sequence has great potential as testing signal in non-destructive testing. Because its autocorrelation is almost a delta function, the sequence can be used for speed of sound assessment. Resulting Impulse response contains very similar data as Impact-echo. Unlike Impact-echo, where strike energy is limited by nonlinear effects, Maximum Length Sequence can deliver virtually unlimited energy over time. Length of the sequence and also signal generation rate is a curtail choice in order to achieve the best results.

Abstract: This paper is focused on clarifying behaviour of concrete at elevated temperature with employing new test set-up constructed at Institute of Building Construction and Technology, Vienna University of Technology. This unique test set-up allows measuring gas permeability of different building materials such as concrete or ceramic at both high temperature (up to 400°C) and pressure (up to 6 bars). Present paper illustrates a new set up for permeability measurement during the heating and cooling and different testing procedures and evaluation of their influence on results.

Abstract: In ultrasonic testing the vibration spectrum must be understood and the measured frequency peaks should match specific sample characteristics. In this paper, the experimental data are compared with results obtained using modal analysis based on Finite Element Method and the vibration was also calculated using classical Euler-Bernoulli approach, which is very simple but somewhat limited. The specimen geometry as well as the material of choice are both very simple to predict, model and measure - i.e. round cross section metal rod. In this case the FEM gives slightly better result that the simplified analytical calculation.

Abstract: Non-destructive acoustic analysis method Impact-echo method as a traditional method for civil engineering was used for this experiment. The paper deals with the applicability of Impactecho acoustic method to testing of cement-based composites prepared from a mix of cement mortar and quartz sand, which were intentionally degraded by high-temperature treatment (in the temperatures range from 200°C to 1200°C). The aim of this paper is introduce the effect of high-temperature degradation. An understanding of microstructure performance relationships is the key to true understanding of material behaviors. The results of non-destructive testing confirmed the different structure of mortar specimens. The subjected to high-temperatures led to absorption of lower frequencies as compared to the reference specimens. A significant decrease of the absorbed frequencies was observed, depending on temperature. The largest decrease occurred after the specimens exposure at 400-600 °C. The effect of heat exposure to the decrease of frequencies was mitigated to the temperature degradation 1200 °C.

Abstract: Increased requirements on environmentally friendly construction process of road structures with emphasis on economical savings and durability of roadways lead to search for new material solutions for pavements. Roller-compacted concrete (RCC) is an ordinary concrete poured and compacted with machines typically used for placement of asphalt pavement layers. Its main advantage is relatively good ratio between mechanical properties and overall costs during construction, operation and maintenance phases. After extensive literature review on the use of RCC in the world, the authors focused themselves on a series of tests of specimens made from RCC mix to verify the main characteristics of the material. Slump, compressive and flexural strength, resistance of concrete to deicing chemicals and resistance to abrasion was tested. The results were assessed from the point of view of exploitation of RCC in pavement structures.

Abstract: Concrete shows extensive degradation when exposed to the external sulfate attack, characterized by ingress of sulfate ions from surrounding medium. This process leads to gradual pH decrease, to expansion, cracking, spalling of concrete, and finally to the complete disintegration of the material. Sulfate attack becomes a major destructor in sewage collection systems where the concrete sewer pipes are exposed to sulfates from wastewater as well as from biogenic activity of bacteria. This paper is focused on the sulfate attack on fine grained concrete where the effect of 0.5% sulfuric acid, simulating biogenic sulfuric acid corrosion, 5% sodium sulfate solution and solution simulating sewage water on various types of concrete has been investigated. The concrete specimens were characterized after exposition to corroding media by their mechanical parameters, microstructure and in the case of H₂SO₄ as the most aggressive corroding solution, the mineralogical composition was also determined by XRD analysis. It was found that the exposition to Na₂SO₄ solution twofold improved flexural strengths of concrete mixes based on Portland and sulfate-resisting cements. Contrary, the exposition to H₂SO₄ solution significantly decreased compressive strengths of all types of concrete.

Abstract: The UHPC (Ultra High Performance Concrete) is a promising material suitable for application in special structures. However, the knowledge on performance of this relatively new material is rather limited. The exceptional mechanical properties of UHPC allow for a modification of the design rules, which are applicable in ordinary or high strength concrete. The research executed already in the Czech Republic showed that the anchorage length of ordinary and prestressing steel may be significantly shorter than that which is usually required in code specifications. This paper deals in more detail with impact of thermal stress on bond of prestressing strands and UHPC. Samples were subjected to the cycling heat/frost device and effect of a number of cycles on final bond behaviour of both UHPC and ordinary concrete were investigated. The article describes differences between ordinary concrete and UHPC.